The resonance of portable electronic devices, such as, mobile phones or tablet PCs, is generated by a resonant device inside the portable electronic device. The earlier resonant device often relies on eccentric rotating mass (ERM) vibration motor to provide resonance.
Recently, a trend is forming by replacing the ERM vibration motor with a linear resonant actuator to serve as the resonant device. The reason is that the linear resonant actuator utilizes electromagnetic effect to generate resonance, which is fast in response and low in power-consumption. Moreover, with the use of ball-bearing design, the resonance frequency can be generated.
However, the magnetic field of the known linear resonant actuator is prone to diverge, and cannot be effectively guided to pointing towards the coils, which results in low utilization efficiency of the magnetic field.
Furthermore, the known linear resonant actuator is unable to make the entire coils completely overlap the magnetic field, which leads to a portion of coils unable to utilize the magnetic field after connected to electricity.
Hence, it is desirable to provide a linear resonant actuator, which is able to improve the density of the magnetic field, and guide the direction of the magnetic field pointing to the coils and effectively using the entire magnetic field.